It is said that an Australian physician and a physicist (both unnamed) reported that they had successfully revived a newborn's heart with an electrode on the skin and a needle electrode which was plunged into the baby's heart. That may have been the first successful defibrillation effort. In 1932, Albert Hyman, a New York cardiologist coined the term “pacemaker” for a device he designed to temporarily electrically stimulate patients hearts of hypothermia and shock patients. Then in 1947 a surgeon, Claude S. Beck, used his experimental defibrillator at the University Hospital in Cleveland, Ohio on a 14 year old boy during an open chest surgery to correct severe deformation of the rib cage. After the ribs were refashioned the patient's heart began fibrillating as the chest wall was being sutured closed. Dr. Beck reopened the chest to expose the fibrillating heart. He then used two electrodes directly on the heart to shock it with 1500 volts of alternating current. The boy recovered.
The field of using electricity to defibrillated and pace hearts took off in about 1950 when a Boston, Mass. physician, Paul Zoll, plunged wires through the skin and into the heart to allow his device to temporarily control the heart. Direct current was used in Dr. Zoll's devices rather then the alternating current used by Dr. Beck. Infection around the wires going through the skin, prevented any long term use of Dr. Zoll's device. Zoll founded Zoll Medical Corporation and developed a number of external pacer and defibrillator versions and brought them to market. All of them used simple high voltage waveforms and none of his models used natural codes.
In 1957 C. Walton Lillehei and Earl Bakken developed a wearable pacemaker with a sling carrier to hold a battery operated device with two electrodes pasted to the skin above the heart or which pierced the skin into the heart. In 1958 at the Karolinska Institute in Stockholm, Sweden a patient named Arne Larson received the first implantable pacemaker. It lasted only a few days but another was put in that lasted several weeks. The inventor Rune Elmqvist invented several improved models that kept Larson's heart beating. Over time 24 ever improved pacemakers by various manufacturers were implanted and the patient lived on into his 80s. None of the above used the natural body generated signals. All used high voltage contrived electrical waveforms.
Today, many models of small implantable pacemaker/defibrillators manufactured by a number of corporations have the ability to sense heart activity and automatically adjust electrical output to the heart to both pace and defibrillate. All of the electrical signals for internal devices are direct current powered and are generally 350 volts to 750 volts for defibrillation and usually start at the lower voltage and increase it during a successive three or four shocks. With each defibrillator shock the voltage is increased until the heart responds or the program reaches the highest output voltage. After a certain number of defibrillator shocks the electrodes implanted into the myocardium may burn the heart muscle and in effect char the tissue to such an extent that the electrodes must be moved to another area. This movement of electrodes to even-less-desirable places on the heart muscle in order to be effective. Over time, the patient can expect the defibrillation event to be less successful or not useful at all.
Pacing is a little more complicated in that some pacers use lower voltages to tickle a heart into compliance with relatively low voltages while other hearts need more powerful shocks to maintain a steady beat. Ostensibly implantable pacemakers are programmable through a variable range delivering approximately between 5 to 44 volts. However, it is not clear from manufacturer's claims what the actual delivered level of voltage or amperage is. All of these devices use simple electrical waveforms that bear no resemblance to the actual signals that operate the heart naturally. All natural signals that control the pacing rate are less than a volt. Voltage is not the entire story since impedance and current flow also play a part. The current expressed in amperage is greatly higher in all the state-of-the-art commercial pacemakers than natural currents. Natural amperage is in the order of milli or micro amps in the signal generating string of neurons which we call a nerve.
In general, medical product manufacturers guard voltage and current data which operate their implantable cardiac treatment products. They prefer that the public and the medical profession not know the real details on voltage and amperage levels. The waveforms used by all commercial implantable defibrillator/pacemakers are simple in form and bear no resemblance to the actual neuro coded signals used by natural human or animal cardiovascular systems. An example of waveforms found in some thorax implantable defibrillators consist of undamped capacitor discharge waveform or critically damped capacitor discharge (Edmark) or under-damped capacitor discharge (Lown) types. None of these waveforms resemble the natural neuro coded signals that naturally, from the beginning of life, operate & regulate cardiac operations.
The present invention relates to control of the heart, in particular defibrillation, pacing, and cardiac paralysis by means of an implantable device.
Existing devices for treating cardiac arrhythmia require deployment of high voltages which can, and often do, cause injury to the patient. The present invention permits utilization of low voltages and greatly decreases the risk of further injury to the patient. For example, the voltage required to propel the actual code through tissue and other barriers may be as high as 7 volts, but the actual code will be received by the heart or nerves controlling the heart typically at a range of less than one volt.
An arrhythmia is any abnormal electrical contraction of the heart. Particular arrhythmias include: asystole—no beat at all or “flat-line” on monitor; bradycardia—slow beat, less than 60 beats per minute; tachycardia—fast beat, over 100 beats per minute; and fibrillation—life threatening chaotic heart action in which the heart twitches or quivers rapidly and is unable to pump efficiently.
During fibrillation, less blood is circulating and thus all systems of the human or animal body are at risk. The longer fibrillation continues unchecked the more likely death will occur. For every minute of fibrillation, a 10% reduction of life potential is subtracted, i.e., ten minutes results almost certain death. During fibrillation the electrical system of the heart is disorganized and erratic. The normal rhythmic beat is totally lost. Serious life threatening events begin to occur. Breathing becomes erratic and then stops as electrical failure begins. Shortly the inadequate circulation of blood causes organs and tissues to be oxygen starved and cell death begins. When brain and heart muscle oxygen starvation reach crisis points they begin to die and hence the entire body begins to die. At some point the heart fibrillations are not reversible and death of the human or animal occurs. It is important to stop fibrillation and to restart or regain the same level of heart contractions to oxygenate the entire body properly.
Fibrillation is currently typically treated by an electronic defibrillator which delivers a shock via two hand-held paddles. This process is familiar to those who view medical television shows and witness a shock so great that the entire body jumps. This shock is about 1,800 to 5,600 volts for external shocks and 310 to 750 volts for internal defibrillators. Repeated use of such large electrical shocks likely may damage the nervous system to such an extent that disabilities shall be present even if the patient lives. The popular misconception is that a defibrillator “puts” a heart beat into a stopped heart. Actually, a defibrillator stops the quivering heart, after which, but not always, the heart may resume a slow beat (bradycardia). Paramedics then can use medications to speed up the heart and/or administer an emergency external pacemaker while transporting the victim to a hospital.
In the science of electromyography there is as graphical presentation of fibrillation on a visual monitor of a heart muscle being affected by a monophasic, biphasic or triphasic spike usually of 25 to 100 microvolts in amplitude and each less than 2 milliseconds in duration. These represent uncoordinated contractions of heart muscle (myocardium) fibers. This is a degrading and dangerous state and does require electrical intervention plus oxygen and cardiac medications in an effort to stabilize or regain a normal heart beat. Perhaps 40% of heart attack victims are in fibrillation when a paramedic arrives. Another 40% might be in bradycardia, tachycardia or asystolic status. The other 20% might have plugged heart blood vessels, bleeding, or other conditions that are not related to the electrical function of the heart muscle.
All individual organs of the body are electrochemical in nature and operate on something approximating one volt to conduct their respective duties. Certainly the action of the myocardium (muscular contractile body of the heart) which contracts about one billion times in a life span, also conducts its business of pumping blood utilizing only about one volt of electricity at any point in time. Each beat is a cascading flow of myocardial contractile motions that squeeze blood from the four chambers of the heart and then accept a refilling of blood for the next cycle.
The heart is a pump with a closed system of arteries and veins with a natural duty to circulate oxygenated blood over the entire network of blood vessels. Oxygenated blood is red when it is rich with oxygen loaded into its red cells, called erythrocytes. Blood turns blue as carbon dioxide (CO2) and other waste products are loaded into its red cells, not now called “blue cells.” The returning blue blood is pumped to the lungs to release the CO2and other gaseous waste products. The red cells immediately uptake oxygen and continue their journey via the heart and into the blood vessels, to cyclically do it all over again.
State of the art application of electricity for medical therapy to stop the fibrillation or quivering that is often encountered when a paramedic arrives on the scene of a heart attack victim, uses from 1,800 to 5,600 volts with 27 to 75 amps of current. The actual voltage and amperage that reaches the heart varies under Ohm's law by the resistance of the human or animal body and the integrity of electrode contacts to the body. Ohm's law states that voltage (V) equals the product of current (I) and resistance (R), or V=IR. Hydration of the skin under the electrodes also plays into the efficiency of the electrical therapy. There is approximately 50 to 150 ohms of resistance in the body depending on the hydration of live tissues. However, the most outer thin layer of dry skin can be 1000 to 30,000 ohms or higher. But high voltage can bust through that skin layer. Obviously the tissue is not as good a conductor as a metallic wire. However, because of the ionic nature of human or animal bodies it is possible to generate a specific waveform and cause it to enter the biological tissue and have an effect. Designers of external defibrillators anticipate a 50-ohm resistance load, but they know it could be somewhat higher. Internal implantable defibrillators/pacers operate in the highly conductive millei of the body inside the skin.
Despite public perception, most of the people collapsing with heart failure, are not reached in time by paramedics to save them. Those that live because they received early defibrillation are often impaired from the cardiopulmonary resuscitation (CPR) process or by the high-voltage energy applied to their chest. The use of voltages that are in the range of 1,800 to 5,600 volts applied to the closed-bare chest of a human is a risky event. It is also risky to the medical personnel who must stop all contact with the patient or potentially be an electrocution victim themselves. The patient must sustain the large shock which conducts all over the body, with risk of burning out peripheral nerves and injuring any organ or system. There is a question of why such large voltage electric shock therapeutically even makes a positive outcome in the small minority of heart attack victims it saves.